Evaluating the Rationality of Managers' Sales Forecasts

This paper deals with the analysis and evaluation of sales forecasts of managers, given that it is unknown how they constructed their forecasts. Our goal is to find out whether these forecasts are rational. To examine deviations from rationality, we argue that one has to approximate how the managers could have generated the forecasts. We describe several ways to construct these approximate expressions. The analysis of a large set of a single manager's forecasts for sales of pharmaceutical products illustrates the practical usefulness of our methodology.evaluating forecasts;intuition;rationality;fixedevent forecasts;forecast updates;sales forecasts

Quantum dynamics in high codimension tilings: from quasiperiodicity to disorder

We analyze the spreading of wavepackets in two-dimensional quasiperiodic and random tilings as a function of their codimension, i.e. of their topological complexity. In the quasiperiodic case, we show that the diffusion exponent that characterizes the propagation decreases when the codimension increases and goes to 1/2 in the high codimension limit. By constrast, the exponent for the random tilings is independent of their codimension and also equals 1/2. This shows that, in high codimension, the quasiperiodicity is irrelevant and that the topological disorder leads in every case, to a diffusive regime, at least in the time scale investigated here.Comment: 4 pages, 5 EPS figure

The Ammann-Beenker tilings revisited

This paper introduces two tiles whose tilings form a one-parameter family of tilings which can all be seen as digitization of two-dimensional planes in the four-dimensional Euclidean space. This family contains the Ammann-Beenker tilings as the solution of a simple optimization problem.Comment: 7 pages, 4 figure

High-Tc bolometers with silicon-nitride spiderwebsuspension for far-infrared detection

High-Tc GdBa2Cu3O7-δ (GBCO) superconducting transition edge bolometers with operating temperatures near 90 K have been made with both closed silicon-nitride membranes and patterned silicon-nitride (SiN) spiderweb-like suspension structures. As a substrate silicon-on-nitride (SON) wafers are used which are made by fusion bonding of a silicon wafer to a silicon wafer with a silicon-nitride top layer. The resulting monocrystalline silicon top layer on the silicon-nitride membranes enables the epitaxial growth of GBCO. By patterning the silicon-nitride the thermal conductance G is reduced from about 20 to 3 μW/K. The noise of both types of bolometers is dominated by the intrinsic noise from phonon fluctuations in the thermal conductance G. The optical efficiency in the far infrared is about 75% due to a goldblack absorption layer. The noise equivalent power NEP for FIR detection is 1.8 pW/√Hz, and the detectivity D* is 5.4×1010 cm √Hz/W. Time constants are 0.1 and 0.6 s, for the closed membrane and the spiderweb like bolometers respectively. The effective time constant can be reduced with about a factor 3 by using voltage bias. Further reduction necessarily results in an increase of the NEP due to the 1/f noise of the superconductor

Child abuse: a common problem in Curaçao?

Objective: To assess the prevalence of child abuse among high school students in Curacao. Methods: A questionnaire survey among high school students up to 17 years of age was conducted. The questionnaire was based on existing literature and validated questionnaires. The questionnaire used was analysed and adapted to the situation in Curacao by a panel of experts on child abuse. The primary objective was to gain insight into the incidence, prevalence and various forms of child abuse among students in Curacao. Five forms of child abuse are distinguished in the literature: physical abuse, emotional abuse, sexual abuse, neglect and exploitation. Furthermore, the degree of confidence of the students in general practitioners (GPs) as care providers in the field of child abuse was explored. Results: Questionnaires from 545 of the 628 respondents were included. In total, 43% of the respondents had ever-experienced an event which could be defined as (a form of) child abuse. More than one-third of the respondents reporting child abuse ever had an experience that could be interpreted as physical abuse. More than 15% of the respondents reporting child abuse had experienced sexual abuse. Girls experienced significantly more sexual abuse than boys. Emotional abuse in the last year was experienced by 3% of the respondents. One per cent of the respondents ever-experienced neglect. According to most respondents, GPs were not seen as care providers in cases of child abuse; they believed that GPs were mainly to be consulted for illnesses or physical symptoms and not for forms of child abuse. Conclusion: The prevalence of ever-having-experienced a form of child abuse is estimated at 431 per 1000 students. Child abuse, particularly physical abuse, is common in Curacao, and is probably comparable to other surrounding countries. General practitioners were not seen as care providers in identifying and reporting cases of child abuse according to most respondents